Apollo 9 and Apollo 10: preparing for landing

Our Apollo article series is getting closer to humanity’s first steps on the moon, taken during Apollo 11. Before that, though, we’re going to take a look at Apollo 9 and Apollo 10. These crewed missions tested the spacecraft’s lunar module, making sure that Neil Armstrong and Buzz Aldrin would be able to land safely on the moon’s surface a few months later.

Apollo 9

Apollo 9 launched on 3 March 1969. The crew were commander Jim McDivitt, lunar module pilot Rusty Schweickart and command module pilot Dave Scott. Scott would return to space two years later as the commander of Apollo 15, so we’ll be talking more about him in a later article.

Although Apollo 8 had travelled all the way to the moon, the Apollo 9 mission was conducted closer to home. Apollo 9 flew in low Earth orbit, its altitude varying between about 200 and 500 km. For comparison, the International Space Station, which had its first launch about three decades later, orbits at an altitude of about 400 km.

This was the first mission to test the performance of the Apollo spacesuit outside a spacecraft. Schweickart went out into space in the suit and spent a little under an hour spacewalking, ensuring that the suit’s life support systems functioned correctly. This suit would later be used by astronauts walking on the moon.

It was absolutely essential for the spacesuits to work correctly. In order for the Apollo astronauts to survive on the moon’s surface, their suits needed to address many different issues. You can learn about some of the Apollo spacesuit’s functions in our first Apollo article.

Apollo 9 was also the first flight to take the Apollo lunar module into space. The lunar module was the part of the spacecraft that was designed to take the astronauts down to the moon’s surface and return them to the main spacecraft afterwards. It wouldn’t be anywhere near the moon on this occasion, but the mission was an opportunity to ensure it could be flown as expected.

During the mission, the crew detached the lunar module from the command and service module, which formed the main body of the Apollo spacecraft. McDivitt and Schweickart flew the lunar module for several hours before docking with the main spacecraft and joining Scott in the command module.

Before detaching the lunar module, the crew also tested the lunar module’s engine while docked to the main spacecraft, to see whether the lunar module could provide backup propulsion for the spacecraft as a whole if the main engine in the service module failed. During the later Apollo 13 mission, that possibility of engine trouble became a reality. After an explosion in the service module compromised the spacecraft’s fuel cells, the Apollo 13 crew had to rely on the lunar module’s engine to get them safely home. In a later article, we’ll talk in more depth about Apollo 13.

Apollo 10

Apollo 10 took off on 18 May 1969, crewed by commander Tom Stafford, lunar module pilot Gene Cernan and command module pilot John Young. Young and Cernan would later command their own missions to the moon; Young walked on the lunar surface during Apollo 16, and Cernan during Apollo 17.

Each Apollo mission had its own name for the spacecraft. In the case of Apollo 10, the command module was named Charlie Brown and the lunar module was named Snoopy, after the characters from the Peanuts comic strip. It’s not the only time Snoopy has been to space; he was also aboard Artemis I in the form of a soft toy.

Apollo 10 was essentially a full rehearsal for the planned moon landing during Apollo 11. The spacecraft reached the moon and went into lunar orbit. Stafford and Cernan took the lunar module close to the moon’s surface and returned in it to the main spacecraft, as if they were performing a moon landing, although they didn’t actually land; at their closest point, they were about 14 km from the moon. NASA wanted to be certain that everything would work as expected for the actual landing.

There was an alarming moment when Stafford and Cernan fired the lunar module’s engines and, due to an incorrectly positioned switch, the module started spinning wildly. This was a case of human error, which is something that also affects Earth-based vehicles and which self-driving vehicles may help to reduce. Fortunately, they were able to get the situation under control and returned safely to the main spacecraft.

The Apollo 10 crew returned to Earth at 39,938 km/h: the fastest speed at which humans have ever travelled. The rehearsal had been a success, and, with the knowledge gathered from this mission and the ones preceding it, humanity was finally ready to land on the moon.

Two months later, during Apollo 11, Neil Armstrong would become the first person to step onto the lunar surface. We’ll talk more about that mission in the next article of our Apollo series.

Cover image: NASA

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